Semiconductor integrated circuit (IC) technology has experienced rapid progress including the continued minimization of feature sizes and the maximization of packing density. The minimization of feature size relies on improvements in photolithography and its ability to print smaller features or critical dimensions (CD). However, a photomask used in photolithography may suffer an angle-dependent CD difference, in which pattern features such as lines may have different widths when disposed from different directions.
Optical proximity correction (OPC) is a technique used in photolithography to compensate for image errors that occur during the lithography process. OPC often has problems in not being able to converge similar dimensions of mask (DOM) in adjacent mask templates. Efforts to improve OPC consistency in adjacent templates often occur at the expense of OPC consistency in individual templates.
It is desired to improve OPC convergence and consistency, as well as achieving a low mask error enhancement factor (MEEF), a low edge placement error (EPE) and good CD uniformity.